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KVM: VMX: Enable io bitmaps to avoid IO port 0x80 VMEXITs 

This patch enables IO bitmaps control on vmx and unmask the 0x80 port to
avoid VMEXITs caused by accessing port 0x80. 0x80 is used as delays (see
include/asm/io.h), and handling VMEXITs on its access is unnecessary but
slows things down. This patch improves kernel build test at around
3%~5%.
	Because every VM uses the same io bitmap, it is shared between
all VMs rather than a per-VM data structure.

Signed-off-by: Qing He <qing.he@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
He, Qing 2007-04-30 09:45:24 +03:00 committed by Avi Kivity
parent 8f41958bdd
commit fdef3ad1b3
1 changed files with 46 additions and 4 deletions
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50
drivers/kvm/vmx.c
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@ -34,6 +34,9 @@ MODULE_LICENSE("GPL");
static DEFINE_PER_CPU(struct vmcs *, vmxarea);
static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
static struct page *vmx_io_bitmap_a;
static struct page *vmx_io_bitmap_b;
#ifdef CONFIG_X86_64
#define HOST_IS_64 1
#else
@ -1129,8 +1132,8 @@ static int vmx_vcpu_setup(struct kvm_vcpu *vcpu)
vmcs_write32(GUEST_PENDING_DBG_EXCEPTIONS, 0);
/* I/O */
vmcs_write64(IO_BITMAP_A, 0);
vmcs_write64(IO_BITMAP_B, 0);
vmcs_write64(IO_BITMAP_A, page_to_phys(vmx_io_bitmap_a));
vmcs_write64(IO_BITMAP_B, page_to_phys(vmx_io_bitmap_b));
guest_write_tsc(0);
@ -1150,7 +1153,7 @@ static int vmx_vcpu_setup(struct kvm_vcpu *vcpu)
CPU_BASED_HLT_EXITING /* 20.6.2 */
| CPU_BASED_CR8_LOAD_EXITING /* 20.6.2 */
| CPU_BASED_CR8_STORE_EXITING /* 20.6.2 */
| CPU_BASED_UNCOND_IO_EXITING /* 20.6.2 */
| CPU_BASED_ACTIVATE_IO_BITMAP /* 20.6.2 */
| CPU_BASED_MOV_DR_EXITING
| CPU_BASED_USE_TSC_OFFSETING /* 21.3 */
);
@ -2188,11 +2191,50 @@ static struct kvm_arch_ops vmx_arch_ops = {
static int __init vmx_init(void)
{
return kvm_init_arch(&vmx_arch_ops, THIS_MODULE);
void *iova;
int r;
vmx_io_bitmap_a = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
if (!vmx_io_bitmap_a)
return -ENOMEM;
vmx_io_bitmap_b = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
if (!vmx_io_bitmap_b) {
r = -ENOMEM;
goto out;
}
/*
* Allow direct access to the PC debug port (it is often used for I/O
* delays, but the vmexits simply slow things down).
*/
iova = kmap(vmx_io_bitmap_a);
memset(iova, 0xff, PAGE_SIZE);
clear_bit(0x80, iova);
kunmap(iova);
iova = kmap(vmx_io_bitmap_b);
memset(iova, 0xff, PAGE_SIZE);
kunmap(iova);
r = kvm_init_arch(&vmx_arch_ops, THIS_MODULE);
if (r)
goto out1;
return 0;
out1:
__free_page(vmx_io_bitmap_b);
out:
__free_page(vmx_io_bitmap_a);
return r;
}
static void __exit vmx_exit(void)
{
__free_page(vmx_io_bitmap_b);
__free_page(vmx_io_bitmap_a);
kvm_exit_arch();
}